Dynamic characterization of humidity-induced perovskite/polyacrylonitrile composite nanofibers based on tilted fiber grating

Humidity performance of perovskites is critical for efficient fabrication and large-scale application of light-emitting devices as it directly influences the material stability, film quality and device lifespan. Herein, we propose an all-fiber strategy for dynamic monitoring of the humidity-induced perovskite/polyacrylonitrile (PAN) composite nanofibers. Pure-bromide quasi-2D perovskite nanocrystals are in situ synthesized and encapsulated in the PAN matrix on the optical fiber platform via an electrospinning technique, which ensure the luminescence stability of the materials in relative humidity (RH) above 50%RH. By wrapping the composite nanofibers around an excessively tilted fiber grating (Ex-TFG) to serve as a humidity-sensitive film, water molecules can rapidly penetrate the nanofiber matrix and interact with the perovskite material, allowing the transmission spectrum of the grating to accurately quantify their concentrations. Experimental results show that the humidity-induced variations in the complex permittivity of the quasi-2D perovskite/PAN composite nanofibers directly reduce the resonant amplitude of the transmitted modes of the Ex-TFG, achieving a top intensity sensitivity of 0.63 dB/%RH. This study introduces an efficient method for incorporating stable perovskites onto fiber-based devices, and also demonstrates a potential for humidity characterization of the luminescent materials through the real time fiber signal monitoring.